Tamehiko Noguchi describes in Journal of Society of Organic Synthetic Chemistry (Yuki Gosei Kagaku Kyoukaishi), vol. 19, p. 920 (1961) and vol. 20, p. 64 (1962) that 4,4′-bis(1,3,5-triazinylamino)stilbene-2,2′-disulfonic acid derivatives are useful as fluorescent brightening agents.
U.S. Pat. No. 2,875,058, No. 2,933,390, and No. 2,945,762 describe 4,4′-bis(1,3,5-triazinyl-amino)stilbene-2,2′-disulfonic acid derivatives are employable as additives for a photographic silver halide emulsion.
German Patent (DE) No. 1,945,316 discloses 4,4′-bis-(1,3,5-triazinylamino)stilbene-2,2′-disulfonic acid derivatives which show high fluorescent brightening effect on cellulose fibers. The disclosed derivatives have a sulfoethylamine substituent group on the 2-position of its triazine ring and additionally a morpholine or alkanolamine substituent group on the 4-position. Examples of the alkanolamines are monoethanolamine, methylethanolamine, diethanolamine, isopropanolamine, and diisopropanolamine.
The 4,4′-bis(1,3,5-triazinylamino)stilbene-2,2′-disulfonic acid derivatives to be employed in the form of aqueous solutions such as photographic silver halide emulsions and aqueous solutions for processing photographic silver halide-containing material are preferably well soluble in water or an aqueous solution. In more detail, the derivatives should be rapidly dissolved in an aqueous medium and then should be hardly deposited during the storage of the aqueous solution.
Japanese Patent Provisional Publications No. 6-329,936 and No. 6-332,127 disclose 4,4′-bis(1,3,5-tri-azinylamino)stilbene-2,2′-disulfonic acid derivatives which are employable as fluorescent brightening agents for an aqueous solution for processing photographic silver halide material. The disclosed derivatives have high solubility in the aqueous solution and are hardly deposited even when the processing solution is kept at low temperatures. The latter 6-332,127 publication indicates that a preferred compound is such derivative that the triazine ring is substituted on its 2-position with ethylamine having a sodium sulfonate salt [therefore, four sodium sulfonate groups are introduced into the derivative] and further substituted on its 4-position with an alkanolamine (e.g., 2-methyethanolamine).